TITLE: Pyroxene HS119 DESCRIPT
MINERAL: Augite (Pyroxene group)
COLLECTION_LOCALITY: Oaxaca, Mexico
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
"I-4 Augite 119B-Oaxaca, Mexico. (Ca, Mg, Fe2+, Fe3+, Ti, Al)2(Si, Al)2O6: Augite is an important ferromagnesian mineral of igneous rocks, and is particularly common in basic rocks. It occurs, but less frequently, in intermediate and ultrabasic rocks. The spectrum is dominated by both Fe2+ and Fe3+ absorptions, which produce a very general broad band centered near 1.0µ. The faint bands near 2.3µ are probably due to hydroxyl combinations even though the 1.4µ band is indiscernible."
Sieve interval 74 - 250µm.
Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1973, Visible and near-infrared spectra of minerals and rocks: VI. Additional silicates. Modern Geology, v. 4, p. 85-106.
40 kV - 30 mA, 7.0-9.5 keV
File: Pxn119.out, -.mdi
References: Borg and Smith (1969); Huebner's reference patterns
Found: Clinopyroxene; weak reflections at 6.5 and 3.14 angstroms; possibly significant intensity maxima at 9.4 and 8.4 angstroms.
Comment: Well crystallized pyroxene. Excellent overall match with diopside patterns, but the lattice spacings are slightly larger than in HS15.3B or endmember diopside, suggesting solid solution with hedenbergite. The relatively high background is consistent with secondary radiation due to iron. The two weak reflections are in the positions of plagioclase unindexed reflections that do not correlate with any of the pyrrhoititerace polytypes suggesting an additional phase.red orientation?
J.S.Huebner, J. Pickrell, T. Schaefer, written communication(USGS 1994)
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
100 vol% Clinopyroxene
tr Calcite (fizz with HCl)
bimodal grain size:
mode 1: 270µm @ 99 vol%
mode 2: 7µm @ 1 vol%
avg grain size = 270 µm Smaller grains coat 20% area lg grains
Prismatic grains have two cleavages at nearly 90 deg angles, inclined extinction, slight green-blue pleochroism, 2V= 70-85 deg, biaxial (+), twinning, length slow. All these properties are consistent with this sample being a clinopyroxene (either augite, omphacite, or fassaite). G. Swayze.
LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib04a r 4092 0.2-3.0µm 200 g.s.= 270µm
LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=